It is known to propel a boat or other watercraft using a water jet apparatus mounted to the hull, with the powerhead being placed inside (inboard) the hull. The drive shaft of the water jet apparatus is coupled to the output shaft of the inboard motor. The impeller is mounted on the drive shaft and housed in a water jet housing, the interior surface of which defines a water tunnel. The impeller is designed such that during motor operation, the rotating impeller impels water rearward through the water tunnel. The thrust propels the boat forward.
In addition, it is known to provide a mechanism for diverting the exiting water flow to one side or the other of a water jet midplane, thereby enabling the boat operator to steer the boat to the left or right during forward propulsion. One such mechanism is a steering nozzle pivotably mounted to the water jet housing and in flow communication with the housing outlet. Preferably the pivot axis of the steering nozzle lies in the water jet midplane. As the steering nozzle is pivoted to the left of a central position, the water flow out of the housing is diverted leftward, producing a thrust which pushes the water jet apparatus and the boat stern to the right, thereby causing the bow of the boat to turn to the left, similarly, the boat bow turns to the right when the steering nozzle is pivoted to the right of the central position.
It is also known to provide a mechanism for reversing the direction of the water flow exiting the steering nozzle. The reverse gate can be pivotably mounted to the steering nozzle, its pivot axis being generally perpendicular to the pivot axis of the steering nozzle. In the up position, the reverse gate is clear of the water flow exiting the steering nozzle. In the down position, the reverse gate is disposed in the path of the exiting water flow. In its simplest embodiment, the reverse gate has a U-shaped channel which reverses the water flow exiting the steering nozzle. In other words, when the steering nozzle is turned to the left, the resulting water flow having rearward and leftward flow components is redirected by the reverse gate to have forward and rightward components. This produces a thrust which pulls the boat rearward and propels the water jet apparatus and boat stern to the left, causing the boat to turn left during rearward movement. Similarly, the boat turns to the right during rearward movement when the steering nozzle is turned to the right. The provision of a steerable reverse gate allows the boat operator to steer in forward and reverse in the same manner that an automobile can be steered.
In accordance with another known design, the reverse gate is not steerable, i.e., the reverse gate is pivotably mounted to the water jet housing. In the up position, the reverse gate is clear of the water flow exiting the steering nozzle; in the down position, the reverse gate obstructs the water flow exiting the steering nozzle and reverses the rearward flow component, but does not reverse the lateral flow component. As a result, when the steering nozzle is turned to the left, the resulting water flow having rearward and leftward flow components is redirected by the reverse gate to have forward and leftward components. This produces a thrust which pulls the boat rearward and propels the water jet apparatus and boat stern to the right, causing the boat to turn to right during rearward movement. Similarly, the boat turns to the left during rearward movement when the steering nozzle is turned to the right. Thus there is a need for a non-steerable reverse gate design which would cause the rearward-moving boat to turn left when the steering nozzle is turned to the left and to turn right when the steering nozzle is turned to the right.